A subset of data read from a graph that appeared in the paper “Decreased Brain Volume in Adults with Childhood Lead Exposure” (Public Library of Science Medicine [May 27, 2008]: e112) was used to produce the following Minitab output, where x 5 mean childhood blood lead level (mg/dL) and y 5 brain volume change

(percentage). (See Exercise 13.19 for a more complete description of the study described in this paper)

Regression Analysis: Response versus Mean Blood Lead Level The regression equation is Response 5 20.00179 2 0.00210 Mean Blood Lead Level Predictor Coef SE Coef T P Constant 20.001790 0.00830320.22 0.830 Mean Blood Lead Level 20.0021007 0.0005743 23.66 0.000

a. What is the equation of the estimated regression line? y^ 5 20.001790 2 0.0021007x

b. For this dataset, n 5 100, x 5 11.5, se 5 0.032, and Sxx 5 1764. Estimate the mean brain volume change for people with a childhood blood lead level of 20 mg/dL, using a 90% confidence interval.

c. Construct a 90% prediction interval for brain volume change for a person with a childhood blood lead level of 20 mg/dL.

d. Explain the difference in interpretation of the intervals computed in Parts

(b) and (c).